Definition of Desaturation Event

This may be a little technical or splitting hairs but my question is this:

Is a desaturation event as monitored during an official sleep study with all the bells and whistles attached defined as a 4% drop from Mean O2 level or from any point that a 4% drop is recorded? Example, Mean or average O2 is say 95% so a desat would be at 91%. But let's say you are at 97% and drop to 94%, would they call that a desat or is the desat started from the mean O2 leavel?

It's a dumb question, I don't expect any answers, I'm an idiot. Just curious. It seems as thought the sleep centers use the mean level and the Oximeter reports such as the gold standard Profox uses any 4% drop regardless of the starting point.

Per http://en.wikipedia.org/wiki/Polysomnography:

"The national insurance program Medicare in the US requires a 4% desaturation in order to include the event in the report."

JohnBFisher wrote:Per http://en.wikipedia.org/wiki/Polysomnography:

"The national insurance program Medicare in the US requires a 4% desaturation in order to include the event in the report."

I THINK Too tall is asking - a 4% drop from what? the mean 02 level? or the level right before it drops 4%?

Sharrykb wrote:

JohnBFisher wrote:Per http://en.wikipedia.org/wiki/Polysomnography:

"The national insurance program Medicare in the US requires a 4% desaturation in order to include the event in the report."

I THINK Too tall is asking - a 4% drop from what? the mean 02 level? or the level right before it drops 4%?

Exactly right, thanks for articulating it better than I.

Too tall wrote:

Sharrykb wrote:

JohnBFisher wrote:Per http://en.wikipedia.org/wiki/Polysomnography:

"The national insurance program Medicare in the US requires a 4% desaturation in order to include the event in the report."

I THINK Too tall is asking - a 4% drop from what? the mean 02 level? or the level right before it drops 4%?

Exactly right, thanks for articulating it better than I.

It is a very good question Too tall! I don't know the answer but maybe someone here does.

Hmm... The following might help: http://www.daveburrows.com/cpap/sleepst ... pstudy.pdf

This explains how to review your sleep study and make sense of the information.

In particular, a respiratory event is associated with a partial (hypopnea) or complete obstruction (obstructive sleep apnea) or a cessation of breathing (central apnea). If during that event that lasts at least 10 seconds and the blood oxygen desaturates by at least 4% (during that time), then you have a bona fide event. Doesn't matter if your start at 99% and go to 95%. Or if you start at 92% and drop to 70%. It's how they interact that's important. If your breathing is so disordered as to cause a desaturation and it is frequent enough (your AHI score is more than 5 events per hour), then you need to have it addressed.

Hope that helps explain what a desaturation event means.